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Melting Antarctic ice will slow a major global deep-ocean current by 40% by 2050


A study warns that melting Antarctic ice will slow a major global current in the deep ocean by 40% by 2050 – and could change the world’s climate in the 20th century.

  • The study indicates a possible collapse of the water circulation system around Antarctica
  • It could have centuries-old implications for the health of the oceans and the marine food web

Melting ice around Antarctica will slow a major global deep-ocean current by 2050 that could have devastating effects on ocean health and the marine food web.

A new study finds that it could change the world’s climate for centuries and accelerate sea level rise.

Scientists warn that if greenhouse gas emissions continue at today’s levels, the current in the deepest parts of the ocean could slow by 40 percent in just 30 years.

The adverse impact would deprive marine life of vital nutrients, alter weather patterns and increase sea levels.

A team of Australian researchers said emissions would need to fall rapidly this decade to avoid these potentially catastrophic consequences.

If they don’t, more marine life may become extinct, the ocean will struggle to absorb and retain heat, and ice loss will accelerate further.

“Hence comes the urgency,” said CSIRO oceanographer Dr. Steve Rintoul, who helped produce the forecast and has spent his career studying how the Southern Ocean around Antarctica affects Earth systems.

Once we slow down the circulation, it’s hard to get it going again. Once we start this, we can’t really change our mind. These changes are irreversible over the time scales of many centuries.

There are very few places in the world that produce water cold and dense enough to sink into the deepest parts of the ocean, but Antarctica has four such locations.

About 250 trillion tons of water sink to depths of less than 13,100 feet (4,000 meters) near the continent each year, thus becoming Very cold water, very salty and rich in oxygen.

However, the increase in Antarctic sea ice melt is pEducation about salinity levels, which makes the water less dense and less able to sink.

This is important because it means that the nutrient-rich waters below are not displaced in the normal way and spread to other locations in the depths of the Indian, Pacific and Atlantic oceans.

Such are the dramatic implications, that surface ecosystems around the world are then robbed of the nutrients of those waters.

“If we limit these nutrient fluxes, and we don’t provide enough nutrients to the basis of the food chain … that will clearly have implications for feeding populations in the coming decades, into the 21st century,” said the UNSW professor. Matthew England, who coordinated the new study.

Dr. Rintoul says the new modeling is considerably more complex than any previous work focused on Antarctica, and that means scientists can have a greater degree of confidence in its predictions.

Simulations show a slowing of the overturning circulation, which then leads to a rapid warming of the oceans.

“Direct measurements confirm that deep ocean warming is already underway,” he added.

Professor England says the same thing is happening for the northern hemisphere, with melting of the Greenland ice sheet causing the North Atlantic to overturn.

“These two water masses (in Antarctica and the North Atlantic) absolutely dominate the venting of all ocean water below a depth of about 1,500 meters (4,900 feet),” he said.

He added that the North Atlantic system has been closed in the past, and scientists believe that it is also heading towards a slowdown and possible collapse in the future.

Professor England said the collapse of both systems would have profound effects on marine ecosystems globally.

The projections have been published in the journal Nature.

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